seaweed. In the midst of the largest of these, increased in importance
by the confluence of several large river channels towards one of the
openings in the sea bank, the city of Venice itself is built, on a
clouded cluster of islands; the various plots of higher ground which
appear to the north and south of this central cluster, have at different
periods been also thickly inhabited, and now bear, according to their
size, the remains of cities, villages, or isolated convents and
churches, scattered among spaces of open ground, partly waste and
encumbered by ruins, partly under cultivation for the supply of the
metropolis.

SECTION VI. The average rise and fall of the tide is about three feet
(varying considerably with the seasons; [Footnote: Appendix III, "Tides
of Venice."]) but this fall, on so flat a shore, is enough to cause
continual movement in the waters, and in the main canals to produce a
reflux which frequently runs like a mill stream. At high water no land
is visible for many miles to the north or south of Venice, except in the
form of small islands crowned with towers or gleaming with villages:
there is a channel, some three miles wide, between the city and the
mainland, and some mile and a half wide between it and the sandy
breakwater called the Lido, which divides the lagoon from the Adriatic,
but which is so low as hardly to disturb the impression of the city's
having been built in the midst of the ocean, although the secret of its
true position is partly, yet not painfully, betrayed by the clusters of
piles set to mark the deep-water channels, which undulate far away in
spotty chains like the studded backs of huge sea-snakes, and by the
quick glittering of the crisped and crowded waves that flicker and dance
before the strong winds upon the unlifted level of the shallow sea. But
the scene is widely different at low tide. A fall of eighteen or twenty
inches is enough to show ground over the greater part of the lagoon; and